This invention relates to a method of manufacturing a flat wiring body used as material for electrical wiring, in which a wiring pattern formed of a single or plurality of narrow-width conductors is sandwiched between a pair of electrical insulating films.
Such a method of manufacturing a flat wiring body has been already proposed by Applicant in the Japanese Patent Application Laid-Open Gazette No.6-68722. In this method, as shown in FIG. 17, a conductor foil b is first laminated on a carrier tape a through a sticking layer, only the conductor foil b is stamped out along a predetermined wiring pattern so as not to mutilate the carrier tape a, and then the conductor foil b is divided into a wiring pattern part c and a conductor remainder part d which is a non-wiring part except for the wiring pattern part c. Next, out of the conductor foil b on the carrier tape a, only the conductor remainder part d is peeled and removed so that only the wiring pattern c is left on the carrier tape a. Then, a first insulating tape (not shown) having an adhesive layer is laminated on the carrier tape a so that the wiring pattern part c is transferred to the first insulating tape based on the superiority of the bonding strength of the adhesive layer of the first insulating tape over the bonding strength of the sticking layer on the carrier tape a. Thereafter, the carrier tape a is rolled up. Then, a second insulating tape (not shown) having an adhesive layer as in the first insulating tape is laminated on the first insulating tape to which the wiring pattern part c is transferred, thereby forming a laminate containing the wiring pattern part. The laminate is stamped out into a desired profile thereby obtaining a flat wiring body.
In the above method, if the carrier tape is not securely held in a flat state in the step of peeling the conductor remainder part, the wiring pattern part may be also peeled together with the conductor remainder part. To deal with this problem, Applicant has proposed another method in the Japanese Patent Application Laid-Open Gazette No.7-6640. In this method, the outer surface of the carrier tape is vacuum-suctioned so that the carrier tape is securely held in a flat state, and at this state the conductor remainder part is peeled.
However, in this proposed method, since the conductor remainder part d has a substantially larger area as compared with the wiring pattern part a (see FIG. 17), a relatively large resistance generates from the sticking layer of the carrier tape when the conductor remainder part is peeled. Therefore, the conductor remainder part must be peeled off with a relatively large tension over the resistance against the peeling. This may tear the conductor remainder part from the intermediate portion and such a large tension may lift even the carrier tape vacuum-suctioned. In addition, since the above resistance against the peeling and the tension act on the peeling position of the conductor remainder part, the conductor remainder part is curved at the peeling position at an acute angle to cause plastic deformation. This may invite a breakage of the conductor remainder part at the peeling position. Such a breakage stops the production line. Further, since warpage and distortion occur at the conductor remainder part due to the plastic deformation, when the conductor remainder parts are recovered and collected, the collected remainder parts are extremely bulky. Accordingly, the collected remainder parts must be compressed to compact them. This requires an extra step for compressing them.
As the sticking layer is heated up, its sticking strength becomes smaller. Accordingly, it may be considered that at the peeling of the conductor remainder part the carrier tape is heated up to reduce the resistance against the peeling. However, if the heating temperature is set very high, the wiring pattern part becomes susceptible to peeling over the limit at the same time. This invites the delamination of the wiring pattern part even by a slight contact, together with the peeling of the conductor remainder part.
Further, in the step of transferring the wiring pattern part c to the first insulating tape, it is necessary that both of them are made secure and close contact with each other to prevent air bubbles from being trapped therebetween.
In view of the foregoing problems, the present invention has been made. An object of the present invention is to securely separate the conductor remainder part from the wiring pattern part thereby facilitating the removal of the conductor remainder part and also securely adhere only the wiring pattern part to the insulating tape in the transferring step.